This invention concerns support arm systems and more particularly support arms of the type comprised of forward and rear articulated arms, each arm consisting of parallelogram linkage which is sprung so as to afford a counterbalancing of the supported load, such counterbalancing being achieved in any of various positions of the articulated support arm to enable stable positioning of the supported load as well as a constant orientation of the supported load for all positions of the support arm.
In copending application Ser. No. 61,135, filed July 26, 1979, there is disclosed such an articulated positioning arm system in which the forward arm spring mounting arrangement affords compactness thereof while enabling the use of conventional springs contained within nested channels comprising the forward arm parallelogram link members.
The general arrangement disclosed consists of the pair of links each pivotally connected at either end to brackets, with a pair of tension springs each connected at one end to one of the links and the other to one of the brackets. The line of action of each spring is such as to create a connecting moment about the pivots to the moment created by the arm weight and supported load. The geometry of the front arm is such that the spring leverage increases as the arm is moved towards the horizontal position to offset the increase in leverage of the supported weight. In order to minimize the degree of spring relaxation occurring during such motion, each spring is connected to its respective bracket at a point laterally offset from the pivot point of the connected link away from the direction of rotation of the link occurring as a result of swinging motion of the arm towards the horizontal position. The offset is designed to achieve a better matching of the torque caused by the supported load with the supporting torque which depends upon combinations of spring tension, the spring rate and the spring moment arm.
This particular spring mounting arrangement is such as to cause a slight unbalance between the counterbalancing force exerted by the springs and the weight of the arm and load in some positions of the arm. Thus, the load cannot be positioned by any angle of the forward arm without some provision being made to compensate for such unbalanced forces.
The aforementioned patent application describes a particular mounting arrangement for the forward arm springs in which the effective point of mounting of the springs is such as to be varied in different ranges of positioning of the forward arm which is such as to compensate for such unbalance which would otherwise occur.
While this does achieve the desired ability to counterbalance through the complete range of arm motion, it would of course be advantageous if such compensation could be provided for without the need for the extra components which are included in this arrangement.
The positioning arm system disclosed in that application is intended for use for supporting relatively heavy loads such as television receivers and which is intended to be sold as an assembly.
The combination of the positioning arm system and the supported load is such as to present a relatively cumbersome assembly and it is advantageous to enable separation of the television receiver from the arm system in order to more easily ship and handle the assembly during installation.
However, since the balancing springs exert a countering moment, the absence of the load necessitates some arrangement for preventing the arm from moving outwardly in the absence of such load if the load initially is not assembled to the arm.
It furthermore would be advantageous to provide relatively convenient methods for installing the television receiver such as to enable quick release in order to reduce the time and effort involved in the installation and also to enable ready removal thereof for servicing, etc. Any such arrangement should of course be preferably of maximum simplicity in order to minimize the manufacturing costs of the device.
Additionally, the forward arm springs are disclosed as being adjustable in order to vary the tension of the springs to precisely balance the supported load. In such cases, if the adjustment is lost during shipping, handling and installation of the device, it would be advantageous to provide a convenient means for adjusting the spring force as necessary in order to provide precise counterbalancing of the particular load.
Also, if the load weight is varied due to installation of differing or additional equipment thereon, it would be advantageous to be enable to carry out such adjustments without disassembly of the forward arm.
Accordingly, it is an object of the present invention to provide an articulated arm system of the general type described in which the forward arm springs are mounted at a point laterally offset from the link pivot point in which the resultant unbalancing of forces does not affect the stability of the support arm system in any position.
It is another object of the present invention to provide such articulated support arm system in which the arm system may be positioned in any of infinite positions with complete stability thereof without appreciably increasing the forces necessitated in moving the supported load from one position to another.
It is a further object of the present invention to provide such articulated support arm system in which a simplified parking lock is provided for securing the forward arm in a folded position such that the supported load may be removed without creating the possibility of unintended extension of the forward arm.
It is yet another object of the present invention to provide such articulated connection by which there is enabled a simplified and easily executed installation procedure for mounting the supported load to the forward arm.
It is still another object of the present invention to provide such support arm system in which a parking brake and supported load connection are related such as to reduce the possibility of removal of the supported load without installation of the parking lock and vice versa.
It is yet another object of the present invention to provide such articulated support arm of the type described wherein an arrangement is provided for enabling ready adjustment of the spring tension in the forward arm to enable convenient adjustment of the counterbalancing force.